KLHL12 Promotes Non-Lysine Ubiquitination of the Dopamine Receptors D4.2 and D4.4, but Not of the ADHD-Associated D4.7 Variant.

Kamila Skieterska,Pieter Rondou,Béatrice Lintermans,Kathleen Van Craenenbroeck,Aldrin V Gomes

doi:10.1371/journal.pone.0145654

Abstract

Dopamine D4 Receptor PolymorphismThe dopamine D4 receptor has an important polymorphism in its third intracellular loop that is intensively studied and has been associated with several abnormal conditions, among others, attention deficit hyperactivity disorder.KLHL12 Promotes Ubiquitination of the Dopamine D4 Receptor on Non-Lysine ResiduesIn previous studies we have shown that KLHL12, a BTB-Kelch protein, specifically interacts with the polymorphic repeats of the dopamine D4 receptor and enhances its ubiquitination, which, however, has no influence on receptor degradation. In this study we provide evidence that KLHL12 promotes ubiquitination of the dopamine D4 receptor on non-lysine residues. By using lysine-deficient receptor mutants and chemical approaches we concluded that ubiquitination on cysteine, serine and/or threonine is possible.Differential Ubiquitination of the Dopamine D4 Receptor Polymorphic VariantsAdditionally, we show that the dopamine D4.7 receptor variant, which is associated with a predisposition to develop attention deficient hyperactivity disorder, is differentially ubiquitinated compared to the other common receptor variants D4.2 and D4.4. Together, our study suggests that GPCR ubiquitination is a complex and variable process.

Highlights

Dopamine is an important neurotransmitter in the mammalian brain that controls many basic processes, such as reward-motivated behavior, emotion, movement, sexual behavior and endocrine regulation, by binding to the specific receptors at the postsynaptic and presynapticPLOS ONE | DOI:10.1371/journal.pone.0145654 December 30, 2015Dopamine D4 Receptor Is Ubiquitinated on Non-Lysine Residues terminal
We have shown that KLHL12 interacts with the polymorphic repeats of the D4 receptor (D4R) and enhances its ubiquitination [8] but this has no influence on receptor degradation [31]
In the present study we investigated which specific residues of the D4R are ubiquitinated by the KLHL12-Cullin3 E3 ligase complex

Summary

Introduction

Dopamine is an important neurotransmitter in the mammalian brain that controls many basic processes, such as reward-motivated behavior, emotion, movement, sexual behavior and endocrine regulation, by binding to the specific receptors at the postsynaptic and presynapticPLOS ONE | DOI:10.1371/journal.pone.0145654 December 30, 2015Dopamine D4 Receptor Is Ubiquitinated on Non-Lysine Residues terminal. The dopamine D4 receptor (D4R) has an important polymorphism in its third intracellular loop (IC3) where a 16-amino acid sequence is repeated 2 to 11 times resulting in different receptor variants referred to as D4.2R to D4.11R [4]. The functional role of this polymorphism is not well characterized but several studies suggest association of the 7-repeat variant (D4.7R) with a predisposition to develop attention deficit hyperactivity disorder (ADHD) [6, 7]. In our previous study we have identified by yeast two-hybride screening a BTB-Kelch protein, KLHL12, which interacts with the polymorphic repeats of the D4R and functions as adaptor in the Cullin3-based E3 ligase complex promoting ubiquitination of the receptor [8]

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